The function of an automatic electro-optical tracker is to measure the alignment error between the line-of-sight to a target and the optical system pointing vector. To achieve this, an area correlation tracker consists of at least two functional subsystems: an area signature detector, and an error processor. The function of the area signature detector is to process the video derived from the tracking sensor, which can either be an imaging sensor, such as a vidicon, or a non-imaging sensor, such as a photomultiplier tube, so as to enhance the characteristics that are required for tracking. The function of the error processor is to compare the location of the target, as defined by the video, with some reference and to extract an estimate of the misalignment between the target line-of-sight and the optical system pointing vector.
Area trackers synthesize area signatures, characteristic of the terrain features within a segment of the sensor field-of-view, in order to track areas containing targets whose distinguishing characteristics are not prominent, due to conditions such as camouflage. Upon initiation of tracking, an area tracker stores a reference area signature in a memory, and then derives angular pointing errors based upon the results of a comparison between subsequent area signatures and the earlier memorized reference. An area tracker will track stationary targets and because it operates on the terrain features surrounding the target, it has a built-in immunity against enemy countermeasures.
The present invention relates to techniques for obtaining electronic area signatures compatible with circular, polar or cartesian coordinate imaging systems, such signatures being used for automatic tracking and employable for weapon guidance, platform stabilization, intrusion detection, fire control, and landing aids.